Fundamentals/sinetone-optimized/render.cpp

Using optimized neon functions

This sketch shows how to use the math-neon library which provides optimized implementation of many simple math functions. The code is based on the sinetone/render.cpp project, with the following differences:

• we include libraries/math_neon/math_neon.h instead of cmath
• we call sinf_neon() instead of sinf()
• we can therefore have many more oscillators than in the basic project (just about 90) and we are using them for a weird additive synth

/*
 ____  _____ _        _
| __ )| ____| |      / \
|  _ \|  _| | |     / _ \
| |_) | |___| |___ / ___ \
|____/|_____|_____/_/   \_\
http://bela.io
*/
 
#include <Bela.h>
#include <libraries/math_neon/math_neon.h>
 
float gFrequency = 440.0;
float gPhase;
float gInverseSampleRate;
int gNumOscillators = 120;
float gScale;
 
bool setup(BelaContext *context, void *userData)
{
        gInverseSampleRate = 1.0 / context->audioSampleRate;
        gPhase = 0.0;
    gScale = 1 / (float)gNumOscillators;
        return true;
}
 
void render(BelaContext *context, void *userData)
{
        for(unsigned int n = 0; n < context->audioFrames; n++) {
            float out = 0;
            for(int k = 0; k < gNumOscillators; ++k){
            out += sinf_neon(gPhase) * gScale;
            }
                gPhase += 2.0f * (float)M_PI * gFrequency * gInverseSampleRate;
                if(gPhase > M_PI)
                        gPhase -= 2.0f * (float)M_PI;
 
                for(unsigned int channel = 0; channel < context->audioOutChannels; channel++) {
                        audioWrite(context, n, channel, out);
                }
        }
}
 
void cleanup(BelaContext *context, void *userData)
{
 
}